What needs tweaking? ramming?  

Re: What needs tweaking? ramming?

Trouble free printing score / slice it and forget it:
MK3: A+
MK3 & MMU2: D-

😆 I think it's going to be a long time before we get to "slice it and forget it" with the MMU (or any other multimaterial system). There's just too much that can go wrong, and we're still too early on the experience curve.

But I think we could get to "slice it, tweak a few things, watch the first layer carefully and then check on it every few hours." On a good day my MMU is about at that level.

True.... I like that it gave u a laugh anyway. Some firmware tweaks and we may get closer. They definitely have to figure out a way to detect lack of filament in extruder, not just lack of filament in mmu

Re: What needs tweaking? ramming?

I kinda keep thinking it'd be better to trim the filament every time. Lose less that way than priming.

Re: What needs tweaking? ramming?

This piece of info (more ramming means thicker tips and less stringing, less means thinner tips and more strings) is very useful, but there's like a dozen parameters that condition the shape of the tip.

Can anybody share what do they do? I mean, for example, keeping all the other variables fixed, what is the difference between one two, three or five cooling passes? (i'd say more cooling passes gives you a thicker tip, but I am not so sure. Tests take so long that is difficult to perform many).
Same for all the other parameters: What effect does increasing or reducing the cooling moves speed produce? And the filament load and unload time? What if I increase the printing temp? etc.

In short, I need help to end with the f***ing strings and hairs that always ruin my prints. I ALWAYS get a jam or a loading failure because of faulty tips.

So after three weeks, I am still struggling with this device and the damn strings and hairs, and I have been able to produce zero prints without assistance, so I feel a bit like a beta tester, with the very difference that I paid for the damn machine and I am not being paid to put it to work. The device works like clockwork, except that it does not work.

Re: What needs tweaking? ramming?

You can move the points a little to increase this to 15 mm^3; you need the speed. I ram at a constant 12 mm^3/s, with the heater turned off. Although this is above the V6 maximum, it works quite nicely and produces good tips.

Peter

I'm having issues as well with the stringing, I have very little, and I'm not getting any jams because of it. I'm using Matterhackers Build PLA, and Hatchbox PLA. The problem I'm actually having is with the PTFE tube calibration. I calibrate the PTFE tube with a fresh spool, so the tip is nice and clean, but then after printing, and a tool change, there is a small amount of stringing, and the tip is tapered. Now on the next load of that filament it gets jammed into the bondtech gears, and I can hear gear skipping on the filament in the MMU, and this grinds into the filament leaving a chewed out section. And this can cause issues with loading sometimes on a tool change, the MMU gear catches on that ground out section of filament and fails to load. So I'm trying to get a nice tip on the filament so that there is no stringing or tapered end.

Looking at the ramming graph that you posted, If I understand you correctly, your graph that you use runs straight across at 12 mm^3/s for Volumetric speed? You also say that this is with the "heater turned off"? Not sure what heater? I can't seem to find a heater setting? And you also said that this was above the V6 maximum, what is V6?

Would be nice if someone were to come out with a YouTube video explaining some of the Slic3r settings with regards to Ramming, and give tips on what to adjust in order to get the perfect MMU filament tips. 😀

Thanks in advance. 😀

Re: What needs tweaking? ramming?

I'm having issues as well with the stringing, I have very little, and I'm not getting any jams because of it. I'm using Matterhackers Build PLA, and Hatchbox PLA. The problem I'm actually having is with the PTFE tube calibration. I calibrate the PTFE tube with a fresh spool, so the tip is nice and clean, but then after printing, and a tool change, there is a small amount of stringing, and the tip is tapered. Now on the next load of that filament it gets jammed into the bondtech gears, and I can hear gear skipping on the filament in the MMU, and this grinds into the filament leaving a chewed out section. And this can cause issues with loading sometimes on a tool change, the MMU gear catches on that ground out section of filament and fails to load. So I'm trying to get a nice tip on the filament so that there is no stringing or tapered end.

Looking at the ramming graph that you posted, If I understand you correctly, your graph that you use runs straight across at 12 mm^3/s for Volumetric speed? You also say that this is with the "heater turned off"? Not sure what heater? I can't seem to find a heater setting? And you also said that this was above the V6 maximum, what is V6?

Would be nice if someone were to come out with a YouTube video explaining some of the Slic3r settings with regards to Ramming, and give tips on what to adjust in order to get the perfect MMU filament tips. 😀

Thanks in advance. 😀

Oh, so many questions...

The skipping is because you haven't speed-matched. The initial load in Slic3r needs to be set to about 19 mm/s (or maybe 19.5; not much difference)

I didn't post a graph; and I don't slice with Slic3r. So for me i't easy to ram at max volumetric and play about with temps. There's another thread around here which discusses changing temps in Slic3r. The heater is the extruder heater, which is effectively turned off during ramming (temp set to print - 10 degrees).

The V6 is the E3D V6 hot end used on the Mk3.

Peter

Re: What needs tweaking? ramming?

Oh, so many questions...

The skipping is because you haven't speed-matched. The initial load in Slic3r needs to be set to about 19 mm/s (or maybe 19.5; not much difference)

I didn't post a graph; and I don't slice with Slic3r. So for me i't easy to ram at max volumetric and play about with temps. There's another thread around here which discusses changing temps in Slic3r. The heater is the extruder heater, which is effectively turned off during ramming (temp set to print - 10 degrees).

The V6 is the E3D V6 hot end used on the Mk3.

Peter

Thanks so much Peter, that helps me understand a lot more. 😀

I'll investigate the speed-matching, I'm assuming it has to do with the bontech gear and MMU drive matching speed? I see that "Loading Speed" in all filament settings is set to 14mm/s, so I'll try setting that to 19mm/s and see what happens.

Thanks again for you assistance. 😀

Re: What needs tweaking? ramming?

I don't slice with Slic3r.

What?!? You dont have to use Slic3r for the MMU? What do you use?

Re: What needs tweaking? ramming?

I believe PJR just gives it a little "KISS".

Neal

Re: What needs tweaking? ramming?

I believe PJR just gives it a little "KISS".

Neal

Yup.

Peter

Re: What needs tweaking? ramming?

I'll investigate the speed-matching, I'm assuming it has to do with the bontech gear and MMU drive matching speed? I see that "Loading Speed" in all filament settings is set to 14mm/s, so I'll try setting that to 19mm/s and see what happens.

Yes, that speed-matching, but Slic3r version I have sets "Loading Speed at the Start" to 3 mm/s; this needs to be 19 and the 14mm / sec can be increased to 22.

Peter

Re: What needs tweaking? ramming?

Yes, that speed-matching, but Slic3r version I have sets "Loading Speed at the Start" to 3 mm/s; this needs to be 19 and the 14mm / sec can be increased to 22.

Peter

I haven't tinkered with that setting yet but I'll see if it makes a difference.

If what you say is correct, I'm surprised it hasn't been fixed yet. A simple parameter that's off by such a large factor should be easy to fix and push out.

Re: What needs tweaking? ramming?

If what you say is correct, I'm surprised it hasn't been fixed yet. A simple parameter that's off by such a large factor should be easy to fix and push out.

I think it's because with the right hardware setup (and I don't know what that is) the mismatched speeds have been working in-house and for some users.

Peter

Re: What needs tweaking? ramming?

Yes, that speed-matching, but Slic3r version I have sets "Loading Speed at the Start" to 3 mm/s; this needs to be 19 and the 14mm / sec can be increased to 22.

Peter

Ahhh, the importance of having unique names for your filament profiles. 🙄

I've been tinkering with my problem for most of the day, it's a good thing I have a lot of patients! I have been messing with the loading speeds, and no matter what I did, nothing would change! Then I happened to double check the filament profiles I had selected for the individual filament assignments, and I had the wrong one selected all this time!! I had one filament profile named "Generic PLA MMU2 Less String Test", and another one named "Generic PLA MMU2 Less String Test 2". I was making the changes to the first "String Test", but had "String Test 2" selected on my print!!

Any how, after fixing that goof up, I'm happy to say that the speed settings of 19 mm/s for "Loading Speed at Start", and 14mm/sec "Loading Speed" appears to be working wonderfully at the moment. I found that a "Loading Speed" of 22 was a little to fast, and I would get slight grinding of the Bontech gears. I'm going to start an actual print and see if it will complete without issue. Up till now I've just been printing 5 10mm x 10mm calibration cubes, I found this was the quickest way to test the 5 colors, I would just abort the print after one or two layers.

I also mentioned that I had a small amount of stringing, just a little string at the tip of the filament. I had originally posted a photo of my Ram Settings graph, but I went back to the stock settings. I watched this video on YouTube, , and in this video Chris Warkocki talks about the "Unload Speed at Start" settings. He mentioned that you will have to try either going with a lower number, or a higher number. He explained that different filaments act differently. Some filaments get better with a lower unload speed, some get better. And this varies with color! He suggested to try setting "Unload Speed at Start" to 120, if stringing gets worse, then set it to 80. Doing this method greatly improved what little stringing I had. So I reverted back to the stock graphs for Ram settings.

I hope this helps.

Re: What needs tweaking? ramming?

Rrrrrr! Last night I had things dialed in with regards to my filament tips (at least for the 5 colors I'm currently using), but this morning I wake up to another jam! I cleared the jam, and watched the print, and my tips are fine. But there was a big glob of string stuck in the PTFE tube to the extruder? It got me to thinking, would a filament that has absorbed moisture cause the tips to be inconsistent? I'm printing in PLA, and I know that PLA is less likely to be affected by humidity, but I haven't used these filaments in months (I work out at sea for a couple of months at a time), and they were not hermetically sealed. The successful prints I've had look great, I see no issues in the print that might be caused by hydrated filament? Then again, it might be just inconsistencies with the filament itself that might be causing the random stringing.

Any how, just throwing it out there for some thought. 😀

Re: What needs tweaking? ramming?

I’d like to ask a probably stupid question:

When I am measuring the thickness of my tips I get between 2.00 – 2.10 mm. However, the PTFE tube in the extruder is 1.85 mm in diameter. I don’t understand how the tips can get bigger than 1.85 mm.

Re: What needs tweaking? ramming?

I’d like to ask a probably stupid question:

When I am measuring the thickness of my tips I get between 2.00 – 2.10 mm. However, the PTFE tube in the extruder is 1.85 mm in diameter. I don’t understand how the tips can get bigger than 1.85 mm.

I'm not sure, but I think I've figured out that the "Ramming Settings" determines the shape and thickness of the tip, and not so much the stringing, and I could be utterly wrong about this. 😯

When I was trying to reduce the stringing problem I tried increasing the "Total Ramming Time" in the "Ramming Settings", and I noticed that my tips were much larger than when at a lower ramming time. So I returned to the default setting of 2.50 seconds.

I'm curious as to what your ramming time is?

Re: What needs tweaking? ramming?

2,5 sec. I use PLA/PHA, my tips are looking usually quite good but sometimes still stringing ... Thats enough for small prints but not for bigger prints with > 150 color changes 😥

Re: What needs tweaking? ramming?

I’d like to ask a probably stupid question:

When I am measuring the thickness of my tips I get between 2.00 – 2.10 mm. However, the PTFE tube in the extruder is 1.85 mm in diameter. I don’t understand how the tips can get bigger than 1.85 mm.

Now I'm having the same issue. I switched to using Hatchbox PLA, and I've almost eliminated the stringing, but now I'm getting fat tips and the filament is getting stuck in the PTFE tube. I tried different ram settings, but to no avail. It looks like filament is getting squeezed back up around the tip during the ram sequence. So I'll experiment with some of the other settings (just wished it didn't take so long to do a test print) and see what I come up with. Have you had any luck?

The tip from the extruder is on the left side of the photo, the right side is where I cut it off.

Re: What needs tweaking? ramming?

Decreasing the parameter "Number of cooling moves" made the diameter of my tips smaller. I've set it to 1 move now. Have you tried that ?

Re: What needs tweaking? ramming?

Decreasing the parameter "Number of cooling moves" made the diameter of my tips smaller. I've set it to 1 move now. Have you tried that ?

Yea, that's what I've had it on all this time. 🙁

And during my last test print one of the colors stopped feeding all the way down, almost as if it lost it's PTFE tube length adjustment. So going to start from scratch, so that I get a base line. Then do a test print with each filament using the Generic PLA MMU settings. Then adjust one parameter and do another test print and record what the tips look like. I think I've made so many adjustments all over the place that I've no idea what is affecting what. It's just so frustrating because my issue before was the stringing, I found a PLA that doesn't string much, but now my tips are to thick and wont pull back through the PTFE tube. AND NOW I have one slot that seems to have forgotten it's PTFE length and wont feed the filament down far enough to reach the extruder. I'm so desperately waiting a firmware update, and filament tip guide. I've heard that Prusa is working on one. Will be nice to get a full explanation as to what each parameter does, and what to adjust when we get certain types of filament tips. 😀